*{margin:0; padding:0;}
    body{
        width:100%;
        height:100%;
        background: url(https://gimg2.baidu.com/image_search/src=http%3A%2F%2Ffile06.16sucai.com%2F2016%2F0813%2Ff3b706b71aeedb6109558af94da6d6e6.jpg&refer=http%3A%2F%2Ffile06.16sucai.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1641035271&t=09a372b7f8da627b3532f8defdd00f84);
    }
    .box1{
        width:200px;
        height: 20px;
        border: 1px solid #000;
        background: #fff;
    
    }
    .box2{
        height: 20px;
        background:  red;
    }